Dressings play a major role in wound management, since the moist, warm and nutrient-rich environment of typical wound sites provide ideal conditions for microbial growth. Bacterial colonization and subsequent infection can interfere with the wound healing process by producing various substances (e.g., toxins, proteases and pro-inflammatory molecules) capable of inducing excessive and prolonged inflammatory responses of the host tissues.
Antimicrobial dressings are, for example, used for activity against antibiotic-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative rods, and Candida species. These are the most commonly occurring organisms that cause infections in the use of intravascular and central venous catheters (CVCs) such as intra-venous (IV) catheters, mid-line catheters, dialysis catheters, peripherally-inserted central catheters, chest tubes and so on. Such vascular access catheters are widely used but are associated with catheter-related infection.
Dressings are applied to vascular access sites to minimize the contamination of the insertion site and provide stability of the device. Commercially available intravenous access site dressings (I.V. dressings), such as OpSite® CH (Smith & Nephew, England) or Tegaderm® CHG (3M, USA), include an acrylic-based pressure sensitive adhesive or an adhesive that has similar properties. When repeatedly applied and removed from the same area of the skin surface, e.g. as in the changing of a medical or surgical dressing, or when in place over a prolonged period, such adhesives are apt to remove with them parts of the upper skin layer (the stratum corneum) potentially resulting in skin damage. In addition, these adhesives also fasten strongly to hairs on the skin, often causing pain and discomfort when removing the dressing.
Silicones, as a group, are synthetic polymers containing the recurring group —SiR2O—, wherein R is a radical such as an alky, acyl, phenyl or vinyl group. They are extremely hydrophobic materials with almost no capacity of water uptake, which strongly limits them from fully functioning as a drug releasing wound dressing [Hu et al, Controlled release from a composite silicone/hydrogel membrane, ASAIO 2000; 46: 431-434]. Silicone has been combined with antimicrobial agent(s), such as chlorhexidine digluconate or elemental silver or silver salts. [U.S. Pat. No. 6,572,878; US 2009/0104252].
Due to the properties of silicone, it is difficult to incorporate sufficient amounts of antimicrobial into silicone to achieve a desired antimicrobial activity. Moreover, the amount of antimicrobial used in conjunction with silicone may provide undesirable qualities to the silicone. For example too high an amount of antimicrobial may result in an unworkable and tacky gel or lead to the formation of an opaque gel. All of these characteristics are undesirable.